Bobbin thread guide means

ABSTRACT

Bobbin thread guide means for feeding thread in a zig-zag sewing machine to the needle area from a point along the work feed direction centered with respect to the lateral positions of the needle to avoid irregular stitches of variable loop length during zig-zag sewing. The centered first guide point is fixed on a bobbin carrier adjacent the needle, while a second guide point is provided on the carrier diametrically opposite the first guide point, and, in a conventional manner, lateral of the line of work feed. Bobbin thread is manually positioned in the centered guide point for zig-zag sewing, and is manually withdrawn from this first guide point and allowed to be fed laterally to the work area from the second guide point to avoid hitch stitches during straight sewing.

United States Patent [191 Hamlett [451 July 15,1975

[73] Assignee: White Sewing Machine Company, Cleveland, Ohio 22 Filed: July 5,1974

21 Appl. No.: 485,825

Primary ExaminerGeo. V. Larkin Attorney, Agent, or FirmMcNenny, Farrington, Pearne & Gordon [57] ABSTRACT Bobbin thread guide means for feeding thread in a zigzag sewing machine to the needle area from a point along the work feed direction centered with respect to the lateral positions of the needle to avoid irregular stitches of variable loop length during zig-zag sewing. The centered first guide point is fixed on a bobbin carrier adjacent the needle, while a second guide point is provided on the carrier diametrically opposite the first guide point, and, in a conventional manner, lateral of the line of work feed. Bobbin thread is manually positioned in the centered guide point for zig-zag sewing, and is manually withdrawn from this first guide point and allowed to be fed laterally to the work area from the second guide point to avoid hitch stitches during straight sewing.

5 Claims, 6 Drawing Figures 1 BOBBIN THREAD GUIDE MEANS BACKGROUND OF THE INVENTION The invention relates to improvements in domestic sewing machines and, more specifically, to bobbin thread guide means for zig-zag sewing machines.

PRIOR ART In the use of prior lock stitch sewing machines, imperfect stitches may be produced during zig-zag operation where the loop length of successive stitches varies. Such stitch variation is particularly noticeable and undesirable for reasons of appearance in satin stitch patterns or similar patterns where full width zig-zag operation is employed with a short feed stroke.

The irregular stitch structure apparently results from a lack of balance in the feed path between the bobbin and the alternate stitch positions of the needle. Conventionally, in a zig-zag machine, the bobbin is arranged in a vertical axis rotatable loop taker laterally of the line of work feed through the mid position of the needle. Consequently, length and angularity of the bobbin thread path relative to the feed path depend on the position of the needle. The resulting change in geometry between successive stitches is reflected as a recurrent variation in the stitch loop lengths.

One approach to avoiding this problem is disclosed in U.S. Pat. No. 3,693,565 to S. .I. Ketterer. A disadvantage of the arrangement proposed in this patent is a required cooperation of various structurally and functionally independent elements of the machine, including certain areas of the loop taker. The arrangement proposed by the patent is somewhat complex, and requires tooling and other manufacturing changes and cannot be readily incorporated in existing machines by the user.

U.S. patents in the field of the invention include U.S. Pat. Nos. 2,900,940 and 2,966,130 to R. E. Johnson; U.S. Pat. Nos. 3,373,707 and 3,693,566 to S. .I. Ketterer; and U.S. Pat. No. 3,702,102 to B. R. Davidson et al.

SUMMARY OF THE INVENTION The invention provides guide means on a bobbin carrier of a domestic zig-zag sewing machine for symmetrically directing the bobbin thread to the stitching station. The bobbin thread is fed on the carrier from a point centered along the direction of work feed and the mid position of the needle to produce balanced bobbin thread feed conditions between lateral positions of the needle. The guide means of the invention, by manual selection, allows the bobbin thread alternatively to be fed laterally to the needle in a generally conventional manner to avoid irregular hitch stitches during normal zig-zag sewing.

In the preferred embodiment, the bobbin thread guide means comprises a pair of guide points fixed on opposite sides of the bobbin thread carrier adjacent the plane of the upper side of the bobbin. During zig-zag sewing, the bobbin thread is directed through both of the guide points, while, during normal sewing, the

. thread is directed through only one of the guide points.

As disclosed, the invention is readily embodied by modification of a conventional type of bobbin carrier so that the invention may be implemented with a minimum of tooling and manufacturing expenditures. Preferably, a conventional guide point on the bobbin carrier is maintained and an additional point is provided diametrically opposite to it and proximate to the needle. The invention may be employed in existing machines already in the field through substitution of a bobbin carrier incorporating the invention for a conventional bobbin carrier by the machine user without physical alteration of other parts of the machine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a vertical axis, rotating loop taker and bobbin assembly of a conventional sewing machine;

FIG. 2 is a plan view of the work area of the sewing machine, illustrating the bobbin thread extending from the guide means of the invention to a stitch point at one side of the stitch pattern;

FIG. 3 is a view similar to FIG. 2, showing a bobbin thread at an opposite side of the stitch pattern;

FIG. 4 illustrates an irregular zig-zag stitch pattern produced by a conventional bobbin thread guide;

FIG. 5 is a view similar to FIG. 4, but with a uniform stitch pattern provided by the bobbin thread guide means of the invention; and

FIG. 6 is a perspective, schematic view of a sewing machine illustrating the environment of the work area of FIGS. 2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT A work area, generally designated at 10 in FIG. 6, of a domestic zig-zag lock stitch sewing machine 11 includes a throat plate 12 and a slide cover plate 13. The slide plate 13 is manually movable forwardly, with reference to the position of the operator during use, away from the throat plate 12 to provide access to a loop taker and bobbin assembly, designated generally at 14 in FIG. 1, beneath the plane of the plates 12 and 13.

The loop taker and bobbin assembly 14 includes a rotating loop taker 16, a bobbin carrier 17, and bobbin 18. A bobbin carrier retainer bracket 19 releasably holds the bobbin carrier 17 in an operating position in the loop taker 16, as illustrated in FIGS. 2 and 3. With the exception of the features on the bobbin carrier 17 embodying the invention and described in detail below, the loop taker and bobbin assembly 14 as well as the machine 11 as a whole, are conventional in arrangement and function, and are familiar to those skilled in the art.

The loop taker 16 is a generally cup-shaped body defined by a relatively short cylindrical wall 21 and a lower radial end wall 22. A shaft 23 fixed to the center of the end wall 22 is rotatably mounted and driven about a vertical axis in the machine 11. The shaft 23 drives the loop taker 16 in rot'ation'in timed relation with vertical reciprocation or stitching motion of a needle 26 (FIGS. 2 and 3). The radial wall 22 includes an arcuate slot 27 for passage of the needle 26. A smoothly finished inner peripheral flange 28 is formed adjacent the upper face of the cylindrical wall 21. The flange 28 and wall 21 are interrupted by a slot 29 forming a needle thread loopseizing hook 31. The loop taker 16 is supported by the shaft 23 generally foris provided an inwardly extending radial flange 36 for vertically and rotatably supporting the bobbin 18. A circular flange segment 37 extending in a radial plane on the exterior of the carrier body 33 includes a peripheral groove 38. The surfaces of the groove 38 are adapted to slidingly engage the loop taker flange 28 for vertical support and relative rotation of the bobbin carrier 17 in the loop taker 16.

A first thread guide point 41 is formed as a shallow notch on an upper edge 42 of the carrier 17. Associated with this guide point 41 is a slotted eyelet 43 in the cylindrical carrier wall 33. A thread tension leaf spring 44 is retained on the exterior of the carrier body 33 by a screw 46 and is aligned thereon by a tab 47 received in a hole 48. The tension of the bobbin thread is adjusted by a screw 49 which regulates the force of the spring 44 on a length of bobbin thread between the slotted eyelet 43 and guide point 41 on the exterior of the body 33.

A second bobbin thread guide point 51 is provided by means of a slotted eyelet in a bracket 52. The bracket 52 is conveniently fabricated as a stamping of metal sheet stock and is retained on the circular carrier body 33 by a screw 53. A lower edge 54 of the bracket 52 abuts the carrier flange 37 for alignment purposes. The slotted eyelet or guide point 51 is centered on the plane of the carrier edge 42, which substantially coincides with the plane of a top side 56 of the bobbin 18 when the latter is inserted in the carrier 17.

The disclosed position of the guide means or eyelet 51 relative to the upper extremities of the carrier 17 and bobbin 18 is advantageous for purposes of threading and unthreading the bobbin thread therein. An extension arm 57 of the bracket 52 is inclined downwardly through the plane of the carrier edge 42 to prevent snaring of the needle thread on the bracket 52 during sewing operation. A relief area 58 is formed in the cylindrical body portion 33 and flange 37 of the carrier 17 for finger access and removal of the bobbin 18 from the recess 34. Referring particularly to FIGS. 2 and 3, the bracket 19 releasably retains the bobbin carrier 17 in position and against rotation in the loop taker 16. The bracket 19 is retractable rightwardly and upwardly from the plane of the drawing in FIGS. 2 and 3 from the position illustrated therein for removal together of the carrier 17 and bobbin 18.

With reference to FIGS. 2 and 3, fabric 61 being sewn is fed by a set of feed dogs 62 in a direction indicated by arrows 63, in a conventional manner. The needle 26 operates through an aperture 64 in the throat plate 12 elongated in a direction transverse or lateral to the direction of feed. In zig-zag sewing operations. the needle 26 is reciprocated along its axis in and out of the plane of the drawing of FIGS. 2 and 3, and by conventional means, is laterally oscillated from one side of the aperture 64 to the other, or to some lesser distance or lateral amplitude, depending on the desired width of the stitch pattern. It is desirable for optimum results in the use of the invention that, regardless of amplitude, lateral needle oscillation be centered or symmetrical about a line 66 extending through a r? i position of the needle and parallel to the feed directi'.

In the sewing of zig-zag stitches, a bobbin thread r is routed from the spool 18 outwardly through the 51' ted eyelet 43, axially upwardly between the spring and outer surface of the carrier body 33, inwardly across the guide notch 41, immediately over the top 56 of the bobbin, and through the second guide point or eye 51. In a customary manner, the hook 31 seizes the needle thread loop as it passes the needle 26 and draws a loop of needle thread 68 over the bobbin 18 in the carrier 17 to concatenate the needle thread with the bobbin thread 67. Upon further rotation of the loop taker 16 and hook 31 from the position illustrated in FIGS. 2 and 3, the needle thread loop, designated 69, is released and is subsequently drawn up by a take-up arm (not shown).

As the needle 26 zig-zags and stitches, the bobbin thread 67 is alternately deflected from side to side of the stitch pattern by this drawing up of the needle thread at the point of needle penetration. Study of FIGS. 2 and 3 shows that the path taken by the bobbin thread 67 through either lateral stitch position is of the same length and angularity relative to the direction of feed 63 as that of the other position. This results from the position of the second guide point 51 on line of motion 66 passing through the mid position of the needle 26.

A satin stitch pattern of relatively short feed strokes and wide zig-zag motion, resulting from the use of the central bobbin thread guide point 51, is shown in F IG. 5. As illustrated there, the loops of the needle thread 68 are of substantially uniform length and pleasing appearance. In the prior art, the bobbin thread 67 is customarily fed from a single guide, such as the first guide point 41, directly to the stitching point. Study of FIGS. 2 and 3 shows that the distance and angularity of the bobbin thread feed path are different between the stitching points and this first point 41. Often, the result of this imbalance in bobbin thread feed path length has been an irregular stitch pattern, such as that illustrated in FIG. 4, where the loop lengths of the needle and bobbin threads 68 and 67 are of irregular length and in the case illustrated, the bobbin thread loops have been pulled to the face of the fabric.

When it is desired to produce straight stitching with the machine 11, the bobbin thread 67 is manually removed from the second guide point 51 while it is retained in the first guide point 41. In such a case, the bobbin thread 67 approaches the stitching station in a conventional manner from a point or source lateral of the line 66 of feed through the mid position of the needle 26. The resulting geometry of the approach of the bobbin thread to the stitching point ensures that the needle 26 will reliably descend downwardly past the bobbin thread only on one side of the thread, i.e., to the right of the bobbin thread as viewed in the figures, so that irregular or hitch stitches are avoided.

While I have described my invention in connection with specific embodiments thereof, it is to be clearly understood that this is done only by way of example, and not as a limitation to the scope of my invention as set forth in the objects thereof and in the appended claims.

What is claimed is:

1. In a zig-zag sewing machine, a work area including a throat plate, the throat plate having a needle receiving aperture, means for feeding work along the throat piate in a feed direction, a needle adapted to oscillate laterally of the feed direction from one side of the aperture to the other between stitches, a loop taker mounted on the machine for rotation about a generally vertical axis, the loop taker being disposed below the plane of the throat plate and generally forwardly of the needle aperture, a bobbin carrier, means supporting the bobbin carrier within the rotating loop taker, a bobbin rotatably supported within the bobbin carrier, manually selectable bobbin thread guide means having a first mode for feeding the bobbin thread from a point lateral of the feed path whereby during normal sewing the needle descends on one side of the bobbin thread during successive stitches to avoid irregular stitch formation, said guide means having a second mode for feeding the bobbin from a second point substantially centered on the feed path and mid position of the needle whereby the angularity of the bobbin thread between the second mode feed point and either needle side position in zig-zag sewing operation relative to the feed line is substantially the same and uniform stitch formation is achieved.

2. A zig-zag sewing machine as set forth in claim 1, wherein said manually selectable bobbin thread guide means comprises a first guide point fixed on the bobbin carrier in a zone diametrically opposite the needle and lateral of the feed path through a mid position of the needle, and a second guide point fixed on the bobbin carrier in a zone adjacent the needle and on the line of feed through the mid position of the needle.

3. in a zig-zag sewing machine, a work area including a throat plate, the throat plate having a needle receiving aperture, means for feeding the work along the throat plate in a feed direction, a needle adapted to oscillate laterally of the feed direction from one side of the aperture to the other between stitches, a loop taker mounted on the machine for rotation about a generally vertical axis, the loop taker being disposed below the plane of the throat plate and generally forwardly of the needle aperture, a bobbin carrier, means supporting the bobbin carrier within the rotating loop taker, a bobbin rotatably supported within the bobbin carrier, said bobbin carrier having an upper edge, said bobbin having an upper side substantially coplanar with the upper edge of the bobbin carrier, bobbin thread guide means for feeding the bobbin thread to the needle area, said guide means including a guide eyelet fixed on the bobbin carrier at said upper edge at a point substantially centered on the feed path and mid position of the needie, whereby the angularity of bobbin thread between said point and either needle side position in zig-zag sewing operation relative to the feed line is substantially the same and uniform stitch formation is achieved.

4. A sewing machine as set forth in claim 3, wherein said eyelet is fixed on a side of the bobbin carrier adjacent the needle.

5. A bobbin carrier for a zig-zag sewing machine, comprising a body having a generally cylindrical recess for receiving a bobbin, means on the bobbin carrier for engagement with supporting surfaces of a rotating loop taker and permitting relative rotation therebetween, means in said recess for rotatably supporting a bobbin therein, said body having an upper side substantially coplanar with an upper face of the bobbin received in said recess, thread guide means on said body for directing thread from the bobbin to a stitching station in the machine, a bobbin thread tension adjustment spring on the body, said thread guide means including a first guide point fixed on the body adjacent said thread tension spring, said thread guide means including a second guide point diametrically opposite said first guide point, said second guide point being provided by a slotted eyelet, said slotted eyelet being disposed at said upper side of said body. 

1. In a zig-zag sewing machine, a work area including a throat plate, the throat plate having a needle receiving aperture, means for feeding work along the throat plate in a feed direction, a needle adapted to oscillate laterally of the feed direction from one side of the aperture to the other between stitches, a loop taker mounted on the machine for rotation about a generally vertical axis, the loop taker being disposed below the plane of the throat plate and generally forwardly of the needle aperture, a bobbin carrier, means supporting the bobbin carrier within the rotating loop taker, a bobbin rotatably supported within the bobbin carrier, manually selectable bobbin thread guide means having a first mode for feeding the bobbin thread from a point lateral of the feed path whereby during normal sewing the needle descends on one side of the bobbin thread during successive stitches to avoid irregular stitch formation, said guide means having a second mode for feeding the bobbin from a second point substantially centered on the feed path and mid position of the needle whereby the angularity of the bobbin thread between the second mode feed point and either needle side position in zig-zag sewing operation relative to the feed line is substantially the same and uniform stitch formation is achieved.
 2. A zig-zag sewing machine as set forth in claim 1, wherein said manually selectable bobbin thread guide means comprises a first guide point fixed on the bobbin carrier in a zone diametrically opposite the needle and lateral of the feed path through a mid position of the needle, and a second guide point fixed on the bobbin carrier in a zone adjacent the needle and on the line of feed through the mid position of the needle.
 3. In a zig-zag sewing machine, a work area including a throat plate, the throat plate having a needle receiving aperture, means for feeding the work along the throat plate in a feed direction, a needle adapted to oscillate laterally of the feed direction from one side of the aperture to the other between stitches, a loop taker mounted on the machine for rotation about a generally vertical axis, the loop taker being disposed below the plane of the throat plate and generally forwardly of the needle aperture, a bobbin carrier, means supporting the bobbin carrier within the rotating loop taker, a bobbin rotatably supported within the bobbin carrier, said bobbin carrier having an upper edge, said bobbin having an upper side substantially coplanar with the upper edge of the bobbin carrier, bobbin thread guide means for feeding the bobbin thread to the needle area, said guide means including a guide eyelet fixed on the bobbin carrier at said upper edge at a point substantially centered on the feed path and mid position of the needle, whereby the angularity of bobbin thread between said point and either needle side position in zig-zag sewing operation relative to the feed line is substantially the same and uniform stitch formation is achieved.
 4. A sewing machine as set forth in claim 3, wherein said eyelet is fixed on a side of the bobbin carrier adjacent the needle.
 5. A bobbin carrier for a zig-zag sewing machine, comprising a body having a generally cylindrical recess for receiving a bobbin, means on the bobbin carrier for engagement with supporting surfaces of a rotating loop taker and permitting relative rotation therebetween, means in said recess for rotatably supporting a bobbin therein, said body having an upper side substantially coplanar with an upper face of the bobbin received in said recess, thread guide means on said body for directing thread from the bobbin to a stitching station in the machine, a bobbin thread tension adjustment spring on the body, said thread guide means including a first guide point fixed on the body adjacent said thread tension spring, said thread guide means including a second guide point diametrically opposite said first guide point, said second guide point being provided by a slotted eyelet, said slotted eyelet being disposed at said upper side of said body. 